.middle {
    display: flex;
    justify-content: center;
}

.middle > div {
    width: 900px;
    border: 1px solid gray;
    margin: 50px 0;
}

/*----------------在线留言--------------*/
.online {
    display: flex;
    justify-content: center;
}

.online > div {
    /*border: 1px solid red;*/
    width: 700px;
}

.online > div > div:nth-child(1) {
    margin: 50px 0;
}

.online > div > div:nth-child(1) > div:nth-child(1) {
    display: flex;
    justify-content: center;
    align-items: center;
}

.online > div > div:nth-child(1) > div:nth-child(2) {
    font-size: 10px;
    /*div居中*/
    /*display: flex;*/
    /*justify-content: center;*/
    /*文字居中*/
    text-align: center;
}

/*后代选择器*/
.online .zw {
    color: coral;
    font-size: 40px;
}

.online .yw {
    color: gray;
    font-size: 20px;
}

/*---------------------表单-----------------*/
form {
    /*border: 1px solid red;*/
    width: 500px;
}

.online > div > div:nth-child(2) {
    display: flex;
    justify-content: center;
}

input[type=text] {
    width: 500px;
    background-color: rgb(239, 239, 239);
    border: 1px dashed gray;
    /*line-height: 30px;*/
    padding: 10px;
}

textarea {
    width: 500px;
    background-color: rgb(239, 239, 239);
    border: 1px dashed gray;
    padding: 10px;
    height: 100px;
}

form > div:nth-child(1) > div > div {
    line-height: 30px;
}

/*按钮设置*/
form > div:nth-child(2) {
    display: flex;
    justify-content: center;
}

input[type=submit] {
    background-color: coral;
    color: white;
    /*不要边框*/
    border: none;
    padding: 10px 50px;
    margin: 50px;
}